In general, mobile communication systems have been developed to provide communication while securing the mobility of users. With the rapid development of technologies, mobile communication systems have reached a stage of providing high-speed data communication services as well as voice communication.
Currently, a standardization operation from a 3rd Generation Partnership Project (3GPP) system to a Long Term Evolution (LTE) system is progressing as one of the next generation mobile communication systems. The LTE system is a technology for implementing a high-speed packet based communication having a transmission speed up to 100 Mbps, which is higher than a currently provided data transmission rate, and currently, a standardization of the LTE system is almost finished.
Recently, a discussion for an LTE-Advanced (LTE-A) which improves a transmission speed by combining various new technologies in the LTE communication system is progressing. As a representative technology among newly employed technologies, there is a carrier aggregation. In the carrier aggregation, one terminal uses multiple forward carriers and multiple backward carriers, differently in the prior art in which a terminal transmits/receives data using one forward carrier and one backward carrier.
Currently, only an inter-ENB carrier aggregation is defined in the LTE-A. This causes the application possibility of the carrier aggregation capability to decrease, and thus may cause a problem in which a macro cell and a pico cell cannot be aggregated in a scenario wherein multiple pico cells and one macro cell are overlapped and operated.